Hush: How to upgrade a separating floor’s sound insulation using joist strips

  • 24 Aug 2021

Improving the acoustic performance of separating floors constructed using timber joists can be achieved simply and economically using Hush-Felt 25 joist strips from Hush Acoustics.

These resilient strips provide an effective alternative to using a composite floating floor approach as they are easily stapled to the top of the existing floor joists, prior to laying chipboard, OSB or plywood tongue and groove flooring boards.

When used correctly, they exceed the requirements of all UK Building Regulations – Approved Document E (England & Wales), Section 5 in Scotland and Part G in Northern Ireland.

Suitable for new build and refurbishment projects, and particularly useful in conjunction with many underfloor heating systems, Hush-Felt 25 strips comprise of 140mm x 50mm hardboard slats fixed to a double layer of 10mm Hush-Felt™ resilient layer.


These integral hardboard slats are important as they present the firm, smooth surface needed to support all the most common types of flooring boards.

Installation is simple

In terms of installation, the joist strips are laid end to end, with the hardboard pads facing upwards, and stapled through the Hush-Felt into the joist tops using 16mm staples.

A 10-15mm expansion gap is left around all perimeters, and a snake of Hush-Bond Panel Adhesive is then applied on to each of the hardboard pads for the flooring boards to be laid on top in broken bond fashion. 

At the same time the flooring boards are glued at all tongue and groove joints board to board. Hush-Seal 20 Perimeter Seal is then pressed into the perimeter expansion gap ensuring that the floor floats freely of the walls to maintain acoustic isolation.

Hush-Felt 25 joist strips are integral to many sound insulation systems designed to provide soundproofing between separating floors. These fully tested systems, such as Hush Acoustics’ HD1016: Hush System HF25, which combines the joist strips with Hush-Slab 100 sound absorber fitted in the voids between joists and the Hush-Bar Plus resilient bar system installed on the ceiling below, deliver excellent acoustic treatments.

Range of joist strips

Hush-Felt 25 is one of several options in the Hush Acoustics range of joist strips. An other popular product is Hush-DF 10 joist insulation, which is similar in its approach to Hush-Felt 25 but offers a thinner solution to reduce impact sound transmission through timber internal floors.

When Hush-DF 10 is used in conjunction with Hush-Slab 100 tightly fitted between the joists, along with the correct plasterboard lining, it complies with the internal floor airborne regulations of 40 dB (RW) stated in Approved Document E for England & Wales.

Additional joist treatments available from Hush Acoustics which could be used depending on the separating floor’s construction, include Hush Isolation Tape, a self-adhesive foam/rubber tape attached to the top of joists, and Hush Resilient Seatings, load bearing rubber strips designed to isolate timber joisted construction as well as masonry and metal beam construction.

Find out more about all Hush Acoustics’ sound insulation products and systems at or call 0151 933 2026.

Hush Acoustics Ltd
Unit 2, Tinsley Industrial Estate
Shepcote Way
South Yorkshire
S9 1TH

Tel: 0114 551 8685
Fax: 0151 944 1146

Visit Hush Acoustics' website

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